About Notify Data Size

[kai19960504]

Hi All,

I asked this question before but I accidentally pressed close.

The engineer told me that for nRF5 SDK ( I assume as you said Segger), you can send 10 byte long notification even you have maximum length 50 byte. You do not need to change the maximum length.

According to this answer I have a problem that my array has a mantissa problem.

Generally speaking, I will send 100Bytes of data regularly, but the last Packet may be less than 100Bytes.

If my last Packet is only 20Byte, it will still send 100Byte.

If my last Packet is only 20Byte, it will still send 100Byte.

Best regards,

Kai

[Vidar Berg]

The sd_ble_gatts_hvx() function will not send more data than what is specified by your BLE_Len (ble_gatts_hvx_params_t::p_len) input. So I would suggest you debug the code to check why the BLE_Len is always set to 100 bytes

[kai19960504]

I have tested that changing this will change the amount received each time => add_char_params.max_len = 100; //for array

This seems to have been mandated to send 100Byte each time.

[Vidar Berg]

add_char_params.max_len defines the max. length for the attribute value. You can also specify add_char_params.is_var_len=true; when you add your characteristic if you want to support a variable attribute length. This won't change the size of the notification packet, but it will ensure that the whole attribute value is updated if you send a notification that is less than '.max_len' bytes.

[kai19960504]

Vidar Berg said:

You can also specify add_char_params.is_var_len=true; when you add your characteristic if you want to support a variable attribute length.

That's the answer, thank you so much